Interpretive Summary: Honey bees rely on pollen as a source of protein, vitamins, minerals, and other essential nutrients. When pollen is not available, beekeepers often feed protein supplements. Determining the mechanisms by which honey bees process pollen vs. protein supplements are important in developing and testing the nutritional value of artificial diets. We measured the effects of diet on protein concentration, hypopharyngeal gland development and virus titers in worker honey bees fed either pollen, a protein supplement (MegaBee), or a protein-free diet of sugar syrup. Workers consumed more pollen than protein supplement, but protein amounts and size of hypopharyngeal gland acini did not differ between the two feeding treatments. Bees fed sugar syrup alone had lower protein concentrations and smaller phpopharyngeal glands compared with the other feeding treatments especially as the bees aged. Deformed wing virus was detected in workers at the start of a trial. Virus concentrations were highest in bees fed sugar syrup and lowest in those fed pollen. Overall results suggest a connection between diet, protein levels and immune response.

Technical Abstract:
Elucidating the mechanisms by which honey bees process pollen vs. protein supplements are important in the generation of artificial diets needed to sustain managed honey bees. We measured the effects of diet on protein concentration, hypopharyngeal gland development and virus titers in worker honey bees fed either pollen, a protein supplement (MegaBee), or a protein-free diet of sugar syrup. Workers consumed more pollen than protein supplement, but protein amounts and size of hypopharyngeal glands compared with the other feeding treatments especially as the bees aged. Deformed wing virus was detected in workers at the start of a trial. Virus concentrations were highest in bees fed sugar syrup and lowest in those fed pollen. Overall results suggest a connection between diet, protein levels and immune response.